Fall Protection Apparatus with a Mast and a Boom

ABSTRACT

A fall protection apparatus includes a heavy support base with a pivotal mast having a top member for rotation around the axis of the mast carrying a series of booms pivotal about respective vertical axes, each having an end coupling member for receiving a fall restraint harness. Each boom is formed by a tube which fractures on a fall and an elongate stainless steel strap inside the tube which bends without fracturing. The mast includes a series of telescopic rectangular mast sections with a winch driven cable and pulley arrangement for extending the first section which acts to pull the second inner section to the extended position as the first inner section moves out of the outer section. Each section includes first and second pulleys mounted at the same face of the section with the cable located between the face of the section and the face of the next section.

This application is a continuation in part of application Ser. No.14/847,435 filed Sep. 8, 2015 and claims priority under 35 USC 119 (e)from Provisional application 62/183,964 filed Jun. 24, 2015.

This invention relates to a fall protection apparatus with a telescopicmast where the mast is mounted on a support base and carries a boom atthe upper end onto which a fall restraint harness can be mounted.

BACKGROUND OF THE INVENTION

Upstanding or vertical masts are commonly used to provide an upper endof the mast supported from the ground to which items may be attachedwhich apply a horizontal load to the mast tending to topple the mast toone side.

Where a permanent mounting is required, the mast can be inserted into asleeve which can be connected to the structure of a building or the likeby braces or by burying the sleeve in a concrete floor or otherstructural component.

Portable bases can also be provided which allow the base and the mastcarried thereby to be moved to different locations. However these aretypically metal in construction with various arms and braces so that thebase is complex, massive and difficult to move.

One particular purpose for such masts is that of providing a davitdefining a raised location for connection to a cable of a safety harnessso that the mast can be located adjacent a place of work of a worker forattachment of the cable so that a fall of the worker from an elevatedposition will allow the safety harness to take up the fall before theworker reaches the ground. Of course, in order to achieve this, the mastmust be closely adjacent the place of work to prevent the worker fromswinging toward the mast as he falls. For this purpose preferably thebase is portable, that is it is not attached to the building or localstructure so that it can be lifted and moved.

An arrangement for supporting a fall restraint cable is shown in USPublished Application 2012/0193165 published Aug. 2, 2012 by the presentApplicant. This shows a fall restraint system includes a cable forattachment to a fall restraint harness assembly of a worker. The cablecan be attached to a boom arm cantilevered on a mast carried from theground or can be stretched between two points on opposed walls. A shockabsorber is provided for absorbing at least part of the shock forces soas to reduce the loading applied to the support system. This comprisesan elongate member with a movable member or sleeve mounted on it forlongitudinal movement. The movement is resisted by a friction brake or acompressible material contained within a tube so that the sleeve movesalong the tube in response to loads exceeding the normal load to reducethe loading on the cable while compressing the material in the tube. Thepresent arrangement is particularly designed for use with thearrangement described in this application but can be used to supportmasts for other purposes.

SUMMARY OF THE INVENTION

According to a one aspect of the invention there is provided a fallprotection system comprising:

a support base;

a mast mounted on the base so as to stand upwardly;

a top support member mounted at a top of the mast;

at least one boom attached to the support member and extending outwardlyto one side of the mast;

and a coupling member attached to the boom at the end of the boom forreceiving a fall restraint harness of a worker so that load from a fallis applied to the coupling member;

the boom comprising:

-   -   a tube attached to the support member at an inner end of the        tube and attached to the coupling member at an outer end of the        tube;    -   and an elongate member located inside the tube and attached to        the support member at an inner end of the elongate member and        attached to the coupling member at an outer end of the elongate        member;    -   the elongate member being arranged so that it bends without        fracturing by application of said load applied by a fall to the        coupling member;    -   wherein the tube is of rectangular cross-section with a top        wall, two side walls and a bottom wall;    -   wherein the side walls include at least one weakening        perforation therein arranged adjacent an outer end of the tube        so that said bending of the elongate member commences and        propagates a tearing action of the bottom wall from the side        walls.

In order to best cope right with the bottom wall of the tube, preferablythe elongate member located in the tube at or adjacent the bottom wall.In this arrangement preferably the elongate member is a strap and has awidth substantially equal to a transverse interior width of the tube. Inthis way the elongate member in the fall of the strap lies flat againstthe bottom wall to effect a tearing action along the tube from the outerend as the strap bends.

Preferably the perforation is in the form of a single perforationdefining a slot in the side wall extending along the side wall at a lineof propagation of said tearing action and preferably the side walls eachinclude a slot to propagate the tearing action.

It is of course necessary that the tearing action occurs only at apredetermined load sufficient to require that a fall has taken placerather than a user merely pulling on the cable. For this reason theperforation or slot in the side walls is spaced from the end of the tubeto leave an intact portion of the side wall at the end so that thetearing action commences only at a predetermined load when the intactportion is broken.

An additional advantage in providing the above tearing action is that itprovides an immediately visible indication of the occurrence of a fallthus preventing a user from continuing to use the device. Of course, inany situation, the occurrence of a fall will affect the structure eventhough such changes might not be typically visible. In this case,therefore, the action of the tearing of the tube necessarily provides animmediate visual indication that a fall has taken place requiringreplacement of the structure.

According to another aspect of the invention there is provided a fallprotection system comprising:

a telescopic mast comprising:

a plurality of tubular mast sections including an outer section, a firstinner section slidable longitudinally within the outer section and asecond inner section slidable longitudinally within the first innersection;

each of the sections having a rectangular cross-section so that each hasfirst, second, third and fourth faces parallel to and immediatelyadjacent respective first, second, third and fourth faces of each of theother sections;

the sections being slidable from a retracted position where the firstand second inner sections are at least partly within the outer sectionto an extended position;

a drive arrangement for causing said sliding movement of the first innersection longitudinally of the outer section to the extended positionthereof;

and an extension cable and pulley arrangement for causing the movementof the first inner section to the extended position to be communicatedto the second inner section to cause said sliding movement of the secondinner section longitudinally of the first inner section to the extendedposition thereof;

the extension cable and pulley arrangement including a first extensionpulley and a second extension pulley each mounted on the first innersection and an extension cable arrangement connected at one end to theouter section and at an opposed end to the second inner section so as topull the second inner section to the extended position as the firstinner section moves out of the outer section;

wherein said drive arrangement is arranged also to also cause saidsliding movement of the first inner section longitudinally of the outersection to the retracted position thereof,

said drive arrangement including a retraction cable and pulleyarrangement for causing the movement of the first inner section to theretracted position to be communicated to the second inner section tocause said sliding movement of the second inner section longitudinallyof the first inner section to the retracted position thereof;

said retraction cable and pulley arrangement including a firstretraction pulley and a second retraction pulley each mounted on thefirst inner section and a retraction cable arrangement connected at oneend to the outer section and at an opposed end to the second innersection so as to pull the second inner section to the retracted positionas the first inner section moves into the outer section.

Preferably the first and second pulleys are mounted at the first face ofthe first inner section with the cable arrangement including first andsecond cable lengths each wrapped around a respective one of the firstand second pulleys and extending along the first face of the secondinner section between the first face of the second inner section and thefirst face of the first inner section.

Preferably the first and second retraction pulleys are mounted at thethird face of the first inner section with the retraction cablearrangement including first and second cable lengths each wrapped arounda respective one of the first and second retraction pulleys andextending along the third face of the second inner section between thethird face of the second inner section and the third face of the firstinner section.

While the above definition includes the terms first, second, third andfourth, it is not intended that these be arranged in a particular orderaround the mast and the use of these terms is for convenience ofexplanation only. Where the above definition states therefore that firstand third faces are used, it is not necessary that these are oppositeone another but in many constructions it is preferable that the firstand third faces are opposed, that is the components mounted on the firstand third faces as defined are arranged on opposed faces of the mast.

Preferably the first and second pulleys are parallel and at right anglesto the first face of the first inner section.

Preferably the first and second pulleys are mounted beyond an end of thefirst inner section.

In a suitable mechanical arrangement, the first and second pulleys canbe mounted on a collar attached to an end of the first inner section.

In most constructions for a mast of a suitable height, there is alsoprovided a third inner section inside the second inner section and asecond cable and pulley arrangement for causing the movement of thesecond inner section to the extended position to be communicated to thethird inner section to cause said sliding movement of the third innersection longitudinally of the second inner section to the extendedposition thereof, the second cable and pulley arrangement including athird and a fourth pulley each mounted on the second inner section and acable arrangement connected at one end to the first inner section and atan opposed end to the third inner section so as to pull the third innersection to the extended position as the second inner section moves outof the first inner section; wherein the third and fourth pulleys aremounted at the third face of the second inner section with the cablearrangement including first and second cable lengths each wrapped arounda respective one of the third and fourth pulleys and extending along thethird face of the third inner section between the third face of thethird inner section and the third face of the second inner section.

In this case, in a preferable symmetrical arrangement there is alsoprovided a second retraction cable and pulley arrangement for causingthe movement of the second inner section to the retracted position to becommunicated to the third inner section to cause said sliding movementof the third inner section longitudinally of the second inner section tothe retracted position thereof, the second retraction cable and pulleyarrangement including a third and a fourth retraction pulley eachmounted on the second inner section and a retraction cable arrangementconnected at one end to the first inner section and at an opposed end tothe third inner section so as to pull the third inner section to theretracted position as the second inner section moves into the firstinner section; wherein the third and fourth retraction pulleys aremounted at the first face of the second inner section with theretraction cable arrangement including first and second retraction cablelengths each wrapped around a respective one of the third and fourthretraction pulleys and extending along the first face of the third innersection between the first face of the third inner section and the firstface of the second inner section.

In a preferred construction, the drive arrangement for causing saidsliding movement of the first inner section longitudinally of the outersection to the extended position thereof comprises a drive tube directlyconnected between a coupling on the outer section and the first innersection so as to directly actuate movement there between.

As set forth above, preferably the first and second pulleys beingmounted at the first face of the first inner section with the cablearrangement including first and second cable lengths each wrapped arounda respective one of the first and second pulleys and extending along thefirst face of the second inner section between the first face of thesecond inner section and the first face of the first inner section.

Preferably the first and second pulleys are parallel and at right anglesto the first face of the first inner section. This allows the first andsecond pulleys to be mounted beyond an end of the first inner section ona collar attached to an end of the first inner section.

Preferably there is a third inner section inside the second innersection and a second cable and pulley arrangement for causing themovement of the second inner section to the extended position to becommunicated to the third inner section to cause said sliding movementof the third inner section longitudinally of the second inner section tothe extended position thereof, the second cable and pulley arrangementincluding a third and a fourth pulley each mounted on the second innersection and a cable arrangement connected at one end to the first innersection and at an opposed end to the third inner section so as to pullthe third inner section to the extended position as the second innersection moves out of the first inner section; wherein the third andfourth pulleys are mounted at the third face of the second inner sectionwith the cable arrangement including first and second cable lengths eachwrapped around a respective one of the third and fourth pulleys andextending along the third face of the third inner section between thethird face of the third inner section and the third face of the secondinner section. Thus the third and fourth pulleys are mounted on a sideof the rectangular mast opposite to the first and second pulleys so thatthe construction can collapse to a reduce length. Symmetrically thepulleys of further sections or of the outer section can be arranged atalternate sides of the mast to allow better interleaving of thestructure when collapsed.

In order to ensure proper retraction of the mast when required,preferably the drive arrangement for causing the sliding movement of thefirst inner section longitudinally of the outer section to the extendedposition thereof is arranged also to also cause the sliding movement ofthe first inner section longitudinally of the outer section to theretracted position thereof, the drive arrangement including a retractioncable and pulley arrangement for causing the movement of the first innersection to the retracted position to be communicated to the second innersection to cause said sliding movement of the second inner sectionlongitudinally of the first inner section to the retracted positionthereof; said retraction cable and pulley arrangement including a firstretraction pulley and a second retraction pulley each mounted on thefirst inner section and a retraction cable arrangement connected at oneend to the outer section and at an opposed end to the second innersection so as to pull the second inner section to the retracted positionas the first inner section moves into the outer section.

That is preferably the system includes a retraction cable and pulleyarrangement which is symmetrical to the cable and pulley arrangementwhich causes erection of the mast.

Preferably the first and second retraction pulleys are mounted at thethird face of the first inner section with the retraction cablearrangement including first and second cable lengths each wrapped arounda respective one of the first and second retraction pulleys andextending along the third face of the second inner section between thethird face of the second inner section and the third face of the firstinner section.

Symmetrically as used in the erection system, where there is a thirdinner section inside the second inner section there is preferablyprovided a second retraction cable and pulley arrangement for causingthe movement of the second inner section to the retracted position to becommunicated to the third inner section to cause said sliding movementof the third inner section longitudinally of the second inner section tothe retracted position thereof, the second retraction cable and pulleyarrangement including a third and a fourth retraction pulley eachmounted on the second inner section and a retraction cable arrangementconnected at one end to the first inner section and at an opposed end tothe third inner section so as to pull the third inner section to theretracted position as the second inner section moves into the firstinner section; wherein the third and fourth retraction pulleys aremounted at the first face of the second inner section with theretraction cable arrangement including first and second retraction cablelengths each wrapped around a respective one of the third and fourthretraction pulleys and extending along the first face of the third innersection between the first face of the third inner section and the firstface of the second inner section.

Preferably the first and second cable lengths are mounted at the bottomof the second inner section by a mounting member which allows transferof loads between the first and second cable lengths.

Preferably the mounting member which allows transfer of loads betweenthe first and second cable lengths comprises an arcuate disk member orpart of a disk member carried on the first face of the second innersection for pivotal movement about an axis thereof at right angles tothe first face with the cable lengths wrapped wound an outer peripheryof the arcuate disk member.

Preferably the arcuate disk member is arranged to trap the cable lengthsto prevent escape therefrom. Thus the cable is contained in the areabetween the inner and outer faces of the tubular sections to resist thecable becoming released from its track.

In one arrangement the drive arrangement for causing said slidingmovement of the first inner section longitudinally of the outer sectionto the extended position thereof comprises a drive tube.

However more preferably the drive arrangement for causing said slidingmovement of the first inner section longitudinally of the outer sectionto the extended position thereof comprises a further cable and pulleyarrangement symmetrical to that which elevates the second inner sectionincluding a first further pulley and a second further pulley eachmounted on the outer section and a further cable arrangement connectedat one end to a winch and at an opposed end to the first inner sectionso as to pull the first inner section to the extended position. In thisarrangement preferably the further cable arrangement comprises first andsecond further cable lengths which are mounted at the bottom of thefirst inner section by a mounting member which allows transfer of loadsbetween the first and second further cable lengths and wherein the winchis arranged to simultaneously and symmetrically pull the first andsecond further cable lengths.

Preferably the elongate member is a strap. However other shapes of theelongate member can be used including potentially a cable.

Preferably the elongate member in the form of a flat solid strap ofmetal has a width substantially equal to a transverse interior width ofthe tube.

Preferably the elongate member is stainless steel which has the abilityto bend with predetermined characteristics without the risk of fracture.In this way the tube can be designed to fracture under the load andtherefore the boom collapses inwardly toward the mast so that thedistance of the coupling to which the harness is attached from the mastreduces to reduce the side load on the mast caused by the fall. In thisway total loading on the mast can be reduced so that the dimensions ofthe mast and the support for the mast can be reduced.

Preferably the tube is of rectangular cross-section and the elongatemember in the form of the flat strap is located in the tube at a bottomwall of the tube.

It is of course necessary that the elongate member in the form of thestrap remains connected to the mast at the inner end and to the couplingat the outer end to maintain continuity when the tube fractures. Thuspreferably the tube is fastened to the support member by a pin passingthrough transverse holes in the tube and wherein the elongate memberincludes a hole therethrough by which the elongate member is connectedto the pin. In order to maintain this continuity, as additional wirecable may be attached along the tube on the exterior or on the interiorso that in effect the cable from the harness to the coupling iscontinued right up to the mast by the additional cable. There istherefore no danger of the harness being disconnected from the mast onthe shock loading from a fall even though the worker will fall anadditional distance defined by the length of the boom as he boomcollapses.

The term fracture used in relation to the tube is not limited to anarrangement in which the tube breaks at a specific location across itslength but instead is intended to include any breaking of the tube atany location which occurs due to the load applied in the downwarddirection by the load and due to the bending of the elongate member orstrap.

Preferably therefore in one example, the tube is of rectangularcross-section with a top wall, two side walls and a bottom wall with theelongate member located in the tube at or adjacent the bottom wall, andpreferably the side walls of the tube are arranged adjacent an outer endof the tube so as to commence and propagate a tearing action of thebottom wall from the side walls or at least part of the side walls asthe elongate member or strap bends.

Preferably the tearing action is controlled by and started by theprovision of slots in each of the side walls to propagate the tearingaction.

Preferably the slot in the side walls is spaced from the end of the tubeso that the tearing action commences only at a predetermined load.

Preferably the support member includes an elongate mounting memberinserted into a top end of the mast.

Preferably the elongate mounting member carries a plurality ofupstanding receptacles at spaced positions therearound each forreceiving a respective insert member of a respective one of theplurality of booms.

Preferably each boom includes a swivel coupling for limited side to sidepivotal movement of the boom relative to the elongate mounting memberabout an axis parallel to an upstanding axis of the mast so that thisside to side movement is combined with the free rotation of the insertmember into the upper end of the mast.

Preferably the top support member is removable.

Preferably there is provided a first bracket member attaching the outersection of the mast to the support base for pivotal movement about ahorizontal axis transverse to the mast and an actuator attached to thesupport base for moving the mast between a horizontal stored positionacross the support base to an erected position standing upwardly fromthe support base.

Preferably the support base comprises a rectangular body filled with aballast material and wherein the first bracket member is mounted on oneupstanding side wall of the body.

BRIEF DESCRIPTION OF THE DRAWINGS

One embodiment of the invention will now be described in conjunctionwith the accompanying drawings in which:

FIG. 1 is a side elevational view of a fall restraint apparatusaccording to the present invention showing a mast mounted on a supportbase in the erected position of the mast.

FIG. 2 is a side elevational view of the fall restraint apparatus ofFIG. 1 showing the mast in the folded position of the mast.

FIG. 3 is an isometric view of the mast of FIG. 1.

FIG. 4 is a cross-sectional view along the lines 4-4 of FIG. 3 of themast of FIG. 1.

FIG. 5 is a schematic cross-sectional view similar to that of FIG. 4with the transverse dimensions enlarged to show the construction moreclearly.

FIG. 6 is a cross-sectional view along the lines 6-6 of FIG. 5.

FIG. 7 is a cross-sectional view similar to that of FIG. 4 showing alsothe retraction system symmetrical to the erection system shown in theabove Figures.

FIG. 8 is a top plan view of the top of the mast of FIG. 1 showing twoof the booms.

FIG. 9 is an isometric view of the components of FIG. 8.

FIG. 10 is a cross-sectional view along the lines 9-9 of FIG. 8.

FIG. 11 is a view similar to that of FIG. 10 showing an end portion ofthe boom only and including slots for creating and propagating a tearingaction in the tube.

In the drawings like characters of reference indicate correspondingparts in the different figures.

DETAILED DESCRIPTION

A fall restraint apparatus 10 comprises a support base 11, a mast 12,and a top support member 13 mounted on a top of the mast. The supportbase is preferably of the construction shown in U.S. Pat. No. 8,931,749issued Jan. 13, 2015 of the present Applicant, the disclosure of whichis incorporated herein by reference. In this case the base 11 may bemounted on a wheeled support or vehicle for movement to a requiredlocation, the wheeled support 14 being shown only schematically.

The support member 13 includes at least one and more typically two orfour booms 15 attached to the support member 13 and extending outwardlyto one side of the mast;

As shown in FIG. 10 or 11, each boom 15 includes a coupling member 16 inthe form of a loop 16A attached to the boom at the outer end of the boomfor receiving a fall restraint harness 16C of a worker attached by acable 16B to the loop 16A.

The mast 12 is telescopic so as to extend from the collapsed positionshown in FIG. 2 to the erected position shown in FIG. 1. The telescopicmast includes, as best shown in FIGS. 3 to 6, a plurality of tubularmast sections including an outer section 20, and a plurality of innersections 21, 22 and 23. The number of inner sections can be varied toprovide a required height of the mast. In the schematic illustration asshown as an example in FIGS. 5 and 6 there is provided only a firstinner section 21 slidable longitudinally within the outer section 20 anda second inner section 22 slidable longitudinally within the first innersection 21. It will be appreciated that additional symmetrically mountedfurther sections can be provided including the third inner section 23 ofFIG. 4. Each section has slide collars 24 at the ends so as to provide abearing surface relative to the surrounding section.

Each of the sections has a rectangular cross-section so that each hasfirst, second, third and fourth faces 21A, 21B, 21C and 21D parallel toand immediately adjacent respective first, second, third and fourthfaces of each of the other sections. In this way the sections areslidable from a retracted position where the first and second innersections are at least partly within the outer section to an extendedposition.

A drive arrangement 30 is provided for causing the sliding movement ofthe first inner section 21 longitudinally of the outer section 20 to theextended position thereof, and a cable and pulley arrangement 40 isprovided for causing the movement of the first inner section 21 to theextended position to be communicated to the second inner section 22 tocause said sliding movement of the second inner section longitudinallyof the first inner section to the extended position thereof.Symmetrically a second cable and pulley arrangement 50 is provided forcausing the movement of the second inner section 22 to the extendedposition to be communicated to the third inner section 23 to cause thesliding movement of the third inner section 23 longitudinally of thesecond inner section 22 to the extended position thereof. The drivearrangements provided by the drive 30, the first arrangement 40 and thesecond arrangement 50 are separate and independent of one another andare symmetrical.

Thus the cable and pulley arrangement 30 includes a first and a secondpulley 31, 32 each mounted on the outer section 20 and a cablearrangement 33 connected at one end 33A to the outer section 20 and atan opposed end to the first inner section 21 so as to pull the firstinner section 21 to the extended position. The end 33A of the cablearrangement is connected to a winch 33C and so as to pull the firstinner section to the extended position. The cable lengths 33 are mountedat the bottom of the first inner section 20 by a mounting member 33Dwhich allows transfer of loads between the first and second furthercable lengths. The member 33D comprises an arcuate disk member 33Ecarried on the first face 21A of the first inner section for pivotalmovement about an axis 33F thereof at right angles to the first facewith the cable lengths 33 wrapped wound an outer periphery of thearcuate disk member. Thus unbalanced loads on the cable can be taken upby slight rotation of the disk 33E to prevent excess loading on one partof the cable which could cause breakage. Both cable lengths thereforecontribute equally so that the diameter of the cable can be chosenbearing in mind that only half of the load is applied to each so thatthe cable can be received in the relatively narrow space between thefaces 20A and 21A.

Also the arcuate disk member 33E is arranged to trap the cable lengths33 to prevent escape therefrom by locating the cable in a peripheralchannel and by butting that channel up against the bearing block 24 asshown in FIG. 5. Thus the cable is contained in the area between theinner and outer faces of the tubular sections to resist the cablebecoming released from its track.

The winch 36C is arranged to simultaneously and symmetrically pull thefirst and second further cable lengths 33 so that the load from thewinch acting to extend the mast is applied to both cable lengths.

The first and second pulleys 31 and 32 are mounted at the first face 20Aof the outer section with the cable arrangement 33 including first andsecond cable lengths each wrapped around a respective one of the firstand second pulleys and extending along the first face of the first innersection between the first face of the first inner section and the firstface of the outer section.

The first and second pulleys 31, 32 are parallel and at right angles tothe first face 21A of the first inner section 21. This allows the firstand second pulleys to be mounted beyond an end 20E of the outer section20 on a collar 20F attached to an end of the outer section.

As described above the mast is formed by a series of effectivelysymmetrical stages 30, 40 and 50 where the first stage comprises pulleys31, 32 and cable 33. Symmetrically stage 40 comprises pulleys 41 and 42and a cable 43 and stage 50 comprises pulleys 51, 52 and cable 53.

Thus there is a third inner section 23 inside the second inner section22 and a second cable and pulley arrangement 50 for causing the movementof the second inner section 22 to the extended position to becommunicated to the third inner section 23 to cause said slidingmovement of the third inner section 23 longitudinally of the secondinner section 22 to the extended position thereof, the second cable andpulley arrangement 50 including a third and a fourth pulley 51, 52 eachmounted on the second inner section 22 and a cable arrangement connectedat one end to the first inner section and at an opposed end to the thirdinner section 23 so as to pull the third inner section 2 to the extendedposition as the second inner section moves out of the first innersection.

The third and fourth pulleys 41, 42 are mounted at the third face 22C ofthe second inner section 22. Thus the third and fourth pulleys 41, 42are mounted on a side of the mast opposite to the first and secondpulleys and on an opposite side to the pulleys 51 and 52 so that theconstruction can collapse to a reduce length since the pulleys do notsit one on top of the next. Symmetrically the pulleys of furthersections or of the outer section can be arranged at alternate sides ofthe mast to allow better interleaving of the structure when collapsed.Also as the transverse dimension of the sections reduces, the pulleysare closer together so that again there is more room to bring the heightdown in the collapsed condition.

In one arrangement the drive arrangement for causing the slidingmovement of the first inner section longitudinally of the outer sectioncomprises a drive tube 60 connected between a lug 62 to the outer tubeand a lug 61 connected to the first inner tube.

The apparatus further includes, as part of the drive arrangementincluding the tube 60, directly symmetrical components for driving themast in the downward direction to the retracted position.

Thus the first inner tube is driven downwardly into the outer tube bythe drive tube 60 commencing the retraction of the mast. In some casesthe mast is sufficiently loaded at the top section so that it willnecessarily retract with each section pulling into the next sectionsimply by the force of gravity. However when the load is insufficientall in order to ensure safety to provide controlled retraction of thesections of the mast, there is provided a pair of cable and pulleyarrangements as previously described but operating in oppositedirections for retraction.

In FIG. 7 there is shown the lower end of the mast in the retractedposition including the outer section or tube 71, a first inner tube 70,a second inner tube 69 and the third inner tube 72, all as previouslydescribed.

Thus as shown in FIG. 7 there is a first cable and pulley arrangementgenerally indicated at 63 including a cable 65 fastened to the secondinner tube 69 at a clamp 64 on a bracket 73 attached to the second innertube and wrapped around a pulley 66 carried on a bracket 67 at thebottom end of the first inner tube 70. The cable 65 extends through aspace 74 between the outside surface of the first inner tube and aninside surface of the outer tube 71 up to a disk member 68 on theoutside surface of the first inner tube 70. The disk member 68 isidentical to the disk member 33E and operates in a symmetrical manner.

In this way when the first inner tube 70 is it driven downwardly by thedrive tube 60, its movement is communicated by a downward movement ofthe pulley 66 which pulls the portion of the cable 65 connected to theclamp 64 so as to pull the second in the tube 69 downwardly. In view ofthe symmetry between the cable and pulley arrangement 63 and that thepreviously described cable and pulley arrangements for the erectionmovement, it will be appreciated that the pulley 66 formed one of a pairof pulleys attached to the bracket 67 and that the cable 65 passesaround the disk member 68 the form two parallel runs of the cable.

Thus the drive arrangement includes a retraction cable and pulleyarrangement 63 for causing the movement of the first inner section 70 tothe retracted position to be communicated to the second inner section 69to cause the sliding movement of the second inner section 69longitudinally of the first inner section 70 to the retracted positionthereof. The retraction cable and pulley arrangement 63 includes thefirst retraction pulley and a second retraction pulley 66 each mountedon the first inner section 70 and a retraction cable arrangement 65connected at one end to the first inner section and at an opposed end tothe second inner section so as to pull the second inner section 69 tothe retracted position as the first inner section 70 moves into theouter section 71.

The first and second retraction pulleys 66 are mounted at the third face75 of the first inner section with the first and second cable lengths 65each wrapped around a respective one of the first and second retractionpulleys 66 and extending along the third face 75 of the first innersection between the third face of the first inner section and the thirdface of the outer section.

In order to provide retraction movement of the third inner section tothe fully retracted position with the movement of the second innersection obtained above, there is provided a second retraction cable andpulley arrangement 76 symmetrical to the previously describedarrangements for causing the movement of the second inner section 69 tothe retracted position to be communicated to the third inner section 72to cause the sliding movement of the third inner section 72longitudinally of the second inner section 69 to the retracted positionthereof. The second retraction cable and pulley arrangement 76 a thirdand a fourth retraction pulley 77 each mounted on the second innersection 69 of the bracket 73 and a retraction cable arrangement 78connected at one end to the second inner section and at an opposed endto the third inner section so as to pull the third inner section to theretracted position as the second inner section moves into the firstinner section. In symmetrical manner the third and fourth retractionpulleys 77 are mounted at the first face 79 of the second inner sectionwith the retraction cable arrangement including first and secondretraction cable lengths 78 each wrapped around a respective one of thethird and fourth retraction pulleys 77 and extending along the firstface of the third inner section between the first face of the thirdinner section and the first face of the second inner section up to thedisk member 80.

In this arrangement the first face of the sections is opposite to thethird face of the sections. As previously described, the cable whichcauses the erection is located in the space indicated at 81 between theouter tube and that the first inner tube which is on the first side faceof the structure. The cable which causes the retraction is located inthe space 74 between the outer tube and the first inner tube but at thethird side. In this way the erection and retraction cables are alllocated on the first and third opposing sides.

Turning now to FIGS. 9, 10 and 11, the boom 15 includes an outer tube15A attached to the support member 13 at an inner end and attached tothe coupling member 16 at an outer end. The tube is formed of aluminumor similar material so that it provides structural strength to stand outto the side of the mast but is arranged so that it fractures onapplication of a load applied by a fall to the coupling member causingbending of the tube.

In order to provide structural integrity and continued connection fromthe mast to the coupling 16 in the event of a fall causing fracturing ofthe tube as it bends beyond an allowable angle, there is also provide aninternal elongate member in the form of a flat strap 15B located insidethe tube and attached to the support member at the inner end andattached to the coupling member at the outer end. The flat strap 15B isformed of a flexible metal such as stainless steel which is arranged sothat it bends without fracturing on fracture of the tube. The elongatemember in the form of a flat solid strap of metal has a widthsubstantially equal to a transverse interior width of the tube.Stainless steel which has the ability to bend with predeterminedcharacteristics without the risk of fracture. In this way the tube canbe designed to fracture under the load and therefore the boom collapsesinwardly toward the mast so that the distance of the coupling to whichthe harness is attached from the mast reduces to reduce the side load onthe mast caused by the fall. In this way total loading on the mast canbe reduced so that the dimensions of the mast and the support for themast can be reduced.

The tube 15A is of rectangular cross-section and the flat strap 15B islocated in the tube at a bottom wall of the tube.

It is of course necessary that the elongate member in the form of thestrap remains connected to the mast at the inner end and to the couplingat the outer end to maintain continuity when the tube fractures. Thusthe tube and strap are simultaneously fastened to the support member bya pin 15D passing through transverse holes in the tube and the strap. Inorder to maintain this continuity, an additional wire cable 15E mayoptionally be attached along the tube on the exterior or on the interiorso that in effect the cable from the harness to the coupling iscontinued right up to the mast by the additional cable 15E. There istherefore no danger of the harness being disconnected from the mast onthe shock loading from a fall even though the worker will fall anadditional distance defined by the length of the boom as the boomcollapses.

The pin 15D is carried on a top and bottom plate 15G, 15H strengthenedby a gusset 15J between the tube and the bottom plate 15H. The plates15G and 15H connect to a swivel coupling 15K which allows the boom toswivel in a horizontal plane but an axis parallel to the mast through alimited angle of the order of 70 degrees. The swivel coupling 15K isattached to a vertical tube 15M carried in a sleeve 15N. The sleeve 15Nis attached on one side of the support member 13. Thus the supportmember 13 is removable as a whole from the top of the mast by slidingout of the top section. Also the support member provides a number,typically two or four of the sleeves 15N for receiving the pin 15M ofthe selected number of booms.

As best shown in FIGS. 10 and 11, the tube 15A is rectangular with a topwall 151, a bottom wall 152 and sidewalls 153. The tube extends to anopen end 154. The coupling loop 16A of the attachment 16 is coupled by apin 161 which has ahead 162 and extends through the bottom wall 152 ofthe tube and through the strap 15B to a nut 163 bus connecting thecoupling ring to the bottom wall 152 and the strap 15B.

On application of a load to the ring 16A from a fall of a user, the loadis applied to the pin 161 into the tube and into the strap 15B. The sidewalls 153 are arranged by provision of a slot 154 adjacent an outer endof the tube so as to commence and propagate a tearing action of thebottom wall 152 from the side walls 153 as the elongate member 15Bbends. That is the downward load on the coupling 16 tends to bend thestrap 15B downwardly which is free to bend. However the tube 15A cannotbend with the strap but will instead fracture at a controlled location.In one arrangement this can occur simply as a transverse fracture of thetube for example of the inner end of the tube where it joins the outersupport tube. However more preferably the provision of the slots 164causes a tearing action to commence at the length of the slot so as tocontinue along the direction of the slot to separate the bottom wall 152from the sidewalls 153. This tearing action continues to a distancedepending upon the load applied. This tearing action tends to controlthe bending of the strap so that instead of bending at one location atwhich the tube fractures, instead the tearing action gradually causesthe bend to move along the strap 15B from the end 154 of the tube alongthe tube to the location where the tearing action terminates. It will beappreciated that this downward movement caused by the bending of thestrap moves that the coupling 16 downwardly and toward the mast so as toreduce the mechanical advantage applied by the load to the mast. In thisway the forces on the mast as significantly reduced both by the shockabsorbing effect of the bending of the strap and the by the movement ofthe point of load from the end 154 of the tube toward the mast.

The slot 164 in the side walls has ends 165 and 166 spaced along thelength of the tube by a relatively short distance relative to the fulllength of the tube. Both the structure of the tube is not significantlycompromised during normal support of the coupling 16. The end 165 isspaced from the end 154 of the tube so that the tearing action to leavean intact portion 155 of the tube between the end 165 on the end 154 sothat the intact portion maintains the structure of the tube up to apredetermined load whereupon the tearing action commences only at thepredetermined load. The slot 164 is located close to the adjacent thebottom wall 152 at or adjacent the strap 15B so that only the bottomwall 152 is torn away from the remainder of the tube.

Turning again to FIG. 1, there is provided a first bracket member 11Aattaching the outer section 20 of the mast to the support base 11 forpivotal movement about a horizontal axis at pivot pin 11C transverse tothe mast and an actuator 11D attached to the support base at a bracket11B on the opposite side of the base 11 for moving the mast between ahorizontal stored position shown in FIG. 2 across the support base to anerected position shown in FIG. 3 standing upwardly from the supportbase.

The support base comprises a rectangular body filled with a ballastmaterial and comprising an outer metal wall connected to the bracketsfor transferring the loads from the mast into the support base. The factthat the boom is collapsible reduces the side loading on the mast sothat the support base can hold the mast vertical without toppling andwithout breakage of any of the coupling components.

1. A fall protection apparatus comprising: a telescopic mast comprising:a plurality of tubular mast sections including an outer section, a firstinner section slidable longitudinally within the outer section and asecond inner section slidable longitudinally within the first innersection; each of the sections having a rectangular cross-section so thateach has first, second, third and fourth faces parallel to andimmediately adjacent respective first, second, third and fourth faces ofeach of the other sections; the sections being slidable from a retractedposition where the first and second inner sections are at least partlywithin the outer section to an extended position; a drive arrangementfor causing said sliding movement of the first inner sectionlongitudinally of the outer section to the extended position thereof;and an extension cable and pulley arrangement for causing the movementof the first inner section to the extended position to be communicatedto the second inner section to cause said sliding movement of the secondinner section longitudinally of the first inner section to the extendedposition thereof; the extension cable and pulley arrangement including afirst extension pulley and a second extension pulley each mounted on thefirst inner section and an extension cable arrangement connected at oneend to the outer section and at an opposed end to the second innersection so as to pull the second inner section to the extended positionas the first inner section moves out of the outer section; wherein saiddrive arrangement is arranged also to also cause said sliding movementof the first inner section longitudinally of the outer section to theretracted position thereof, said drive arrangement including aretraction cable and pulley arrangement for causing the movement of thefirst inner section to the retracted position to be communicated to thesecond inner section to cause said sliding movement of the second innersection longitudinally of the first inner section to the retractedposition thereof; said retraction cable and pulley arrangement includinga first retraction pulley and a second retraction pulley each mounted onthe first inner section and a retraction cable arrangement connected atone end to the outer section and at an opposed end to the second innersection so as to pull the second inner section to the retracted positionas the first inner section moves into the outer section.
 2. Theapparatus according to claim 1 wherein the first and second pulleys aremounted at the first face of the first inner section with the cablearrangement including first and second cable lengths each wrapped arounda respective one of the first and second pulleys and extending along thefirst face of the second inner section between the first face of thesecond inner section and the first face of the first inner section. 3.The fall protection apparatus according to claim 1 wherein the first andsecond retraction pulleys are mounted at the third face of the firstinner section with the retraction cable arrangement including first andsecond cable lengths each wrapped around a respective one of the firstand second retraction pulleys and extending along the third face of thesecond inner section between the third face of the second inner sectionand the third face of the first inner section.
 4. The apparatusaccording to claim 3 wherein the first and third faces are opposed. 5.The apparatus according to claim 1 wherein the first and second pulleysare parallel and at right angles to the first face of the first innersection.
 6. The apparatus according to claim 1 wherein the first andsecond pulleys are mounted beyond an end of the first inner section. 7.The apparatus according to claim 1 wherein the first and second pulleysare mounted on a collar attached to an end of the first inner section.8. The apparatus according to claim 1 wherein there is a third innersection inside the second inner section and a second cable and pulleyarrangement for causing the movement of the second inner section to theextended position to be communicated to the third inner section to causesaid sliding movement of the third inner section longitudinally of thesecond inner section to the extended position thereof, the second cableand pulley arrangement including a third and a fourth pulley eachmounted on the second inner section and a cable arrangement connected atone end to the first inner section and at an opposed end to the thirdinner section so as to pull the third inner section to the extendedposition as the second inner section moves out of the first innersection; wherein the third and fourth pulleys are mounted at the thirdface of the second inner section with the cable arrangement includingfirst and second cable lengths each wrapped around a respective one ofthe third and fourth pulleys and extending along the third face of thethird inner section between the third face of the third inner sectionand the third face of the second inner section.
 9. The fall protectionapparatus according to claim 8 wherein there is a second retractioncable and pulley arrangement for causing the movement of the secondinner section to the retracted position to be communicated to the thirdinner section to cause said sliding movement of the third inner sectionlongitudinally of the second inner section to the retracted positionthereof, the second retraction cable and pulley arrangement including athird and a fourth retraction pulley each mounted on the second innersection and a retraction cable arrangement connected at one end to thefirst inner section and at an opposed end to the third inner section soas to pull the third inner section to the retracted position as thesecond inner section moves into the first inner section; wherein thethird and fourth retraction pulleys are mounted at the first face of thesecond inner section with the retraction cable arrangement includingfirst and second retraction cable lengths each wrapped around arespective one of the third and fourth retraction pulleys and extendingalong the first face of the third inner section between the first faceof the third inner section and the first face of the second innersection.
 10. The apparatus according to claim 1 wherein the first andsecond cable lengths are mounted at the bottom of the second innersection by a mounting member which allows transfer of loads between thefirst and second cable lengths.
 11. The apparatus according to claim 10wherein the mounting member which allows transfer of loads between thefirst and second cable lengths comprises an arcuate disk member carriedon the first face of the second inner section for pivotal movement aboutan axis thereof at right angles to the first face with the cable lengthswrapped wound an outer periphery of the arcuate disk member.
 12. Theapparatus according to claim 11 wherein the arcuate disk member isarranged to trap the cable lengths to prevent escape therefrom.
 13. Theapparatus according to claim 1 wherein the drive arrangement for causingsaid sliding movement of the first inner section longitudinally of theouter section to the extended and retracted position thereof comprises adrive cylinder.
 14. A fall protection apparatus comprising: a supportbase; a mast mounted on the base so as to stand upwardly; a top supportmember mounted at a top of the mast; at least one boom attached to thesupport member and extending outwardly to one side of the mast; and acoupling member attached to the boom at the end of the boom forreceiving a fall restraint harness of a worker so that load from a fallis applied to the coupling member; the boom comprising: a tube attachedto the support member at an inner end of the tube and attached to thecoupling member at an outer end of the tube; and an elongate memberlocated inside the tube and attached to the support member at an innerend of the elongate member and attached to the coupling member at anouter end of the elongate member; the elongate member being arranged sothat it bends without fracturing by application of said load applied bya fall to the coupling member; wherein the tube is of rectangularcross-section with a top wall, two side walls and a bottom wall; whereinthe side walls include at least one weakening perforation thereinarranged adjacent an outer end of the tube so that said bending of theelongate member commences and propagates a tearing action of the bottomwall from the side walls.
 15. The apparatus according to claim 14wherein the elongate member located in the tube at or adjacent thebottom wall.
 16. The apparatus according to claim 14 wherein theelongate member is a strap.
 17. The apparatus according to claim 14wherein the elongate member has a width substantially equal to atransverse interior width of the tube.
 18. The apparatus according toclaim 14 wherein the said at least one perforation comprises a slot inthe side wall extending along the side wall at a line of propagation ofsaid tearing action.
 19. The apparatus according to claim 14 wherein theside walls each include a slot to propagate the tearing action.
 20. Theapparatus according to claim 14 wherein the said at least oneperforation in the side walls is spaced from the end of the tube toleave an intact portion of the side wall at the end so that the tearingaction commences only at a predetermined load when said intact portionis broken.